Accurate and robust analysis of challenging environmental samples for regulatory compliance

Significance of the Topic

Environmental monitoring of soil and water is critical for assessing human and ecological exposure to toxic elements such as lead, arsenic, cadmium and persistent organic pollutants. Analytical methods capable of handling complex, high-matrix samples with minimal downtime are essential to meet regulatory standards (e.g. US EPA Method 6020B) and support large-scale testing in contract laboratories.

Objectives and Study Overview

This study demonstrates a robust workflow for the analysis of challenging environmental samples—soil digests and diverse water types—using the Thermo Scientific iCAP RQplus ICP-MS. The goal was to increase instrument uptime and maintain data quality over a continuous 12-hour sequence encompassing more than 160 unknown samples, while complying with EPA 6020B requirements.

Methodology

Samples consisted of ten soil digests (including NIST SRMs) prepared by microwave-assisted aqua regia digestion, and five water matrices (wastewater, brackish and groundwater) analyzed in technical replicates. Calibration of 24 elements used seven standards in 2% HNO₃/0.5% HCl, with online addition of internal standards (Li, Sc, Y, Rh, In, Tb, Ho, Bi). Interference removal was achieved by argon gas dilution at the nebulizer plus helium KED mode in a single-mode method. Quality control included blanks (ICB, CCB), calibration verifications (ICV, CCV), interference check solutions (ICS A/B) and SRM analysis, all managed automatically by Qtegra ISDS software.

Instrumental Equipment

• Thermo Scientific iCAP RQplus ICP-MS with iSC-65 autosampler
• MicroMist nebulizer, cyclonic quartz spray chamber
• Nickel-tipped interface cones, quartz torch, 2.5 mm injector
• Argon gas dilution (AGD) and helium collision gas for KED
• RF power 1550 W; cool gas 14 L/min; nebulizer flow 0.26 L/min
• Spray chamber temperature 2.7 °C, sampling depth 10 mm

Main Results and Discussion

• Instrument detection limits met regulatory requirements; calibration linearity R² > 0.9995.
• Interference checks (ICS A/B) showed all analytes within method criteria.
• Continuing calibration verifications maintained 90–110% accuracy across the run.
• SRM recoveries fell within published concentration ranges for both NIST soils.
• Internal standards remained stable at 80–120% over 12 hours with alternating soil and water samples, indicating minimal drift or matrix effects.

Benefits and Practical Applications

• The AGD plus KED workflow enables direct analysis of high-dissolved-solid samples without manual dilution, reducing sample prep steps and instrument maintenance.
• Automated QC via Qtegra ISDS accelerates compliance with regulatory protocols and minimizes reruns due to drift or carry-over.
• Single-method capability for soils and various water matrices enhances laboratory throughput and cost-effectiveness.

Future Trends and Potential Applications

Advances may include total-digestion protocols (HF-based) for complete mineral breakdown, integration of machine-learning algorithms for real-time QC alerting, and development of portable ICP-MS platforms for on-site environmental screening.

Conclusion

The iCAP RQplus ICP-MS, combined with argon gas dilution and helium collision gas, provides a robust, accurate and high-throughput solution for regulatory analysis of complex environmental samples, ensuring reliable data over extended runs and diverse matrices.

References

1. U.S. EPA Method 6020B (SW-846)
2. Sample preparation techniques for AAS, ICP-OES, and ICP-MS for regulated testing laboratories, Thermo Fisher Scientific